Valve Timing Control for Hydraulic Machine Backlash
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Solution Overview
Problem
Electronically commutated hydraulic machines (ECMs) experience cycle failures due to transient accelerations and pressure changes, leading to system instability, reduced efficiency, and potential component damage, particularly in drivetrain applications where events like backlash cause sudden shaft accelerations and torque discontinuities.
Innovation Solution
A method of actively controlling valve opening and closing phases in ECMs based on measurements or predictions of temporary shaft accelerations and pressure changes, advancing or retarding the timing of valve control signals to prevent cycle failures, thereby improving the reliability and smoothness of operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If valve timing is optimized for maximum displacement fraction (ADF), then pumping efficiency is improved, but the system becomes more susceptible to cycle failures during transient acceleration events
Solution Approach 1:
The valve timing is made dynamic rather than fixed. The controller adjusts the valve timing based on detected shaft acceleration events, transitioning between a default timing (optimized for displacement) and an alternative timing (more tolerant of transient conditions). This dynamic adaptation resolves the contradiction by allowing the system to maximize productivity during normal operation while switching to a more reliable configuration during transient acceleration events.
Solution Approach 2:
The invention changes the timing parameter of valve actuation based on operating conditions. By detecting shaft acceleration and switching between different timing parameters (default vs. alternative timing), the system can optimize displacement fraction during stable operation while preventing cycle failures during transient conditions, thus resolving the contradiction between productivity and reliability.
2Productivity
If valve control signals are transmitted at default timing, then displacement efficiency is maximized, but transient shaft accelerations cause cycle failures
Solution Approach 1:
The controller detects shaft acceleration events and preemptively switches from default timing to alternative timing before cycle failures can occur. This preliminary anti-action counteracts the harmful effect of transient accelerations by adjusting the valve timing to be more tolerant of the changing conditions, preventing the reverberation phenomenon and cycle failures that would otherwise occur.
Solution Approach 2:
The invention converts the harmful effect of transient shaft accelerations into a useful signal for timing adjustment. By detecting the acceleration event, the system uses this previously harmful transient condition as a trigger to switch to an alternative timing mode that is specifically designed to handle such conditions, thereby converting the harmful factor into a beneficial control signal.
3Productivity
If the high pressure valve closes late in expansion stroke, then displacement fraction increases, but reverberation phenomenon occurs preventing effective motoring cycles
Solution Approach 1:
The high pressure valve timing is made dynamic, switching between default timing (optimized for displacement fraction) and alternative timing (preventing reverberation) based on detected shaft acceleration events. During transient acceleration, the alternative timing ensures the high pressure valve closes early enough to prevent the working chamber from insufficiently decompressing, thereby preventing reverberation while maintaining good displacement fraction during normal operation.
Data Source
AI summary
An electronically commutated hydraulic machine is coupled to a drivetrain. Working chambers of the hydraulic machine are connected to low and high pressure manifold through electronically controlled valves. The phase of opening and closing of the valves has a default. In order to avoid cycle failure due to acceleration events, for example due to backlash in the drivetrain, the phase of opening or closing of the electronically controlled valves is temporarily advanced or retarded from the default timing.